1. Technical Field
The present disclosure relates to a bobbin based on carbon nanotubes, and a loudspeaker using the same.
2. Description of Related Art
A loudspeaker is an acoustic device transforming received electric signals into sounds. The electric signals have enough power to make the sounds audible to humans. There are different types of loudspeakers that can be categorized by their working principle, such as electro-dynamic loudspeakers, electromagnetic loudspeakers, electrostatic loudspeakers and piezoelectric loudspeakers. Among the various types, electro-dynamic loudspeakers have simple structures, good sound quality, and low cost, thus it is most widely used.
Electro-dynamic loudspeakers typically include a diaphragm, a bobbin, a voice coil, a damper, a magnet, and a frame. The voice coil is an electrical conductor, and is placed in the magnetic field of the magnet. By applying an electrical current to the voice coil, a mechanical vibration of the diaphragm is produced due to the interaction between the electromagnetic field produced by the voice coil and the magnetic field of the magnets, to produce sound waves.
To evaluate the loudspeaker, a sound volume thereof is a determining factor. The sound volume of the loudspeaker relates to the power of the electric signals and the conversion efficiency of the energy. It is known that the higher the strength and the Young's modulus, the smaller the density of the bobbin, and the higher the volume of the loudspeaker. However, the material of the bobbin is usually polymer, cloth, non-carbon nanotube paper or composite, which have relatively low strength and Young's modulus. Therefore, the rated power of the conventional loudspeakers is relatively low. In general, the rated power of a small sized loudspeaker is only 0.3 W to 0.5 W. Furthermore, the density of the conventional bobbins is usually large, thereby restricting the improvement of the energy conversion efficiency. Therefore, at present, to increase the rated power and the energy conversion efficiency of the loudspeaker, thereby increasing the sound volume, efforts to improve loudspeakers are focused on increasing the strength and Young's modulus and decreasing the density of the bobbin, that is, to increase the specific strength (i.e., strength/density) and the specific Young's modulus (i.e., Young's modulus/density) of the bobbin.
What is needed, therefore, is to provide a bobbin with high strength and Young's modulus, and a loudspeaker using the same.